Rear suspension apparatus for motor vehicle

ABSTRACT

A rear suspension apparatus for a motor vehicle having a differential gear case ( 2 ) disposed between rear right- and left-wheels ( 1 R,  1 L), which is of a torsion beam type. In the rear suspension apparatus, a central portion ( 12   a ) of a torsion beam ( 12 ) for rotatably supporting the rear right- and left-hand wheels ( 1 R,  1 L) is curved to run along the configuration of the differential gear case ( 2 ), and is disposed at the rear of the differential gear case ( 2 ). A suspension damper ( 16 ) stretched between the torsion beam ( 12 ) and the vehicle body is disposed to be inclined upwardly and forwardly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a rear suspension apparatus fora motor vehicle.

[0003] 2. Description of the Related Art

[0004] Japanese Patent Laid-Open No. 4-283114 discloses a conventionalrear suspension apparatus for a motor vehicle in which, in arear-wheel-drive vehicle, right- and left-hand trailing arms areconnected to each other through a torsion beam extending invehicle-width directions. In the rear suspension apparatus, while a reardifferential gear case for covering a rear differential gear is locatedbetween rear right- and left-wheels because of the rear-wheel drive, inorder to avoid the interference between the torsion beam and the reardifferential gear case, in the aforesaid conventional art, a centralportion of the torsion beam in the vehicle-width directions isprotrusively curved upwardly, that is, the torsion beam is disposed tobypass the rear differential gear case upwardly.

[0005] Furthermore, in the case that a motor vehicle with a considerablyshort front nose recently called RV (Recreational Vehicle) or SUV(Sports Utility Vehicle) is designed as a rear-wheel-drive vehicle, atorsion beam type rear suspension apparatus is employed to lower a floorpanel to the utmost.

[0006] On the other hand, for a motor vehicle, it is desired that thefloor panel in a rear section of the vehicle body does not lower atcollision from its rear side. That is, need exists that various kinds ofparts such as a fuel tank placed under the floor panel in the vehiclebody rear section do not come into contact with the road surface becauseof the lowering of the floor panel at the rear side collision.Particularly, in the case of the aforesaid RV, for example, since thedistance between the rear wheels and the vehicle body rear end portionis short, there is a high possibility that a large external force workson the rear suspension at the rear side collision, and the externalforce at the rear side collision can deform the rear wheels upwardlywith respect to the vehicle body, which results in a relative fall ofthe floor panel.

SUMMARY OF THE INVENTION

[0007] Accordingly, the present invention has been developed with a viewto eliminating the above-mentioned problem, and it is an object of thisinvention to provide a rear suspension apparatus for a motor vehiclewith a torsion beam, which is capable of preventing the fall of thevehicle body at the rear side collision.

[0008] For eliminating the foregoing problem and achieving the purpose,according to a first aspect of this invention, in a rear suspensionapparatus for a motor vehicle having a differential gear case disposedbetween rear right- and left-wheels, which rear suspension is of atorsion beam type, a central portion of the torsion beam in a vehiclewidth direction is bent to extend along a configuration of thedifferential gear case and is disposed at the rear of the differentialgear case, and a suspension damper (absorber) stretched between thetorsion beam and a vehicle body is disposed in a state of being inclinedor tilted forwardly and upwardly (inclined to take a further forwardposition in accordance with advancing upwardly).

[0009] With the first aspect, when an external force from a rear sideworks on the torsion beam at the rear side collision, the suspensiondamper acts as a strut because of being a abrupt external force, and theinclination of the damper causes the torsion beam to shift (bedisplaced) downwardly, so that the rear wheels relatively movedownwardly with respect to the vehicle body, thereby preventing the fallof the vehicle body rear section.

[0010] A second aspect is that, in a rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein a central portion of a torsion beam in awidth direction of said motor vehicle is bent along a configuration ofsaid differential gear case, and is located at the rear of saiddifferential gear case, and wherein said differential gear case has acurved section protruding rearwardly, and said central portion of saidtorsion beam is placed at a lower position than a peak portion of saidcurved section.

[0011] With the second aspect, when an external force from a rear sideworks on the torsion beam at the rear side collision, the torsion beamis brought into contact with the curved section of the rear differentialgear case to be guided to shift downwardly, and the rear wheels shiftdownwardly relative to the vehicle body, which can prevent the fall ofthe body rear section.

[0012] A third aspect is that, in a rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein a central portion of a torsion beam in awidth direction of said motor vehicle is bent along a configuration ofsaid differential gear case, and is located at the rear of saiddifferential gear case, and wherein said central portion of said torsionbeam is formed to be at a higher position than both end portions thereofin said vehicle width direction.

[0013] With the third aspect, when an external force from a rear side isapplied to the torsion beam at the rear side collision, owing to thefact that the central portion is formed to be higher than both the endportions in the vehicle width direction, the torsion beam tends to moreeasily shift downwardly, and the rear wheels shift downwardly relativeto the vehicle body, so that the fall of the vehicle body rear sectionis preventable.

[0014] A fourth aspect is that, in a rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein said torsion beam is connected to saidvehicle body through a lateral link extending in said vehicle widthdirection, and said lateral link is disposed to be inclined up and downin said vehicle width direction, with its upper end portion beingconnected to said vehicle body while its lower end portion beingconnected to said torsion beam.

[0015] With the fourth aspect, when an external force from a rear sideacts on the lateral link and the torsion beam, since the lateral link isplaced to be tilted up and down in the vehicle width direction, thetorsion beam shifts downwardly and the rear wheels shift downwardlyrelative to the vehicle body, thus preventing the fall of the vehiclebody rear section.

[0016] A fifth aspect is that, in a rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein an exhaust pipe extending from an engineis bent for bypassing said torsion beam to pass above said torsion beam,and extends to a rear section of said vehicle body, and a portion ofsaid exhaust pipe rearwardly extending from the curved portion isdisposed to run from above said torsion beam to below said torsion beamto cross said torsion beam, and is inclined downwardly and rearwardly.

[0017] With the fifth aspect, while an external force from a rear sideworks on a portion of the exhaust pipe rearwardly extending from thebent portion at the rear side collision, since this portion is tilteddownwardly and rearwardly, the torsion beam shifts downwardly throughthe exhaust pipe and the rear wheels shift downwardly relative to thevehicle body, so that the fall of the vehicle body rear section ispreventable.

[0018] In addition, although the portion of the exhaust pipe rearwardlyextending from the bent portion is bent in the vicinity of the bentportion, the deformation by this bending reduces the space between thetorsion beam and the bent portion, so that the upward shifting of thetorsion beam is more surely preventable.

[0019] A sixth aspect is that, in a rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein a central portion of a torsion beam in awidth direction of said motor vehicle is bent along a configuration ofsaid differential gear case, and is located at the rear of saiddifferential gear case, and wherein a recessed space formed to a floorpanel of said vehicle body and enlarging protrusively and downwardly isplaced at the rear of said torsion beam, and the height of a lower endportion of a front wall defining said recessed space is set to exceedthe height of an upper end portion of said torsion beam.

[0020] With the sixth aspect, although an external force from a rearside presses the recessed space (or the floor panel forming the recessedspace) forwardly at the rear side collision, since the height of thelower end portion of the front wall defining the recessed space is setto exceed the upper end portion of the torsion beam, the recessed spaceallows the torsion beam to shift downwardly so that the rear wheelsshift downwardly relative to the vehicle body to prevent the fall of thevehicle body rear section.

[0021] A seventh aspect is that, in the motor vehicle rear suspensionapparatus employing the sixth aspect, the front wall extends at leastfrom above the torsion beam to under the torsion beam, and is inclineddownwardly and rearwardly.

[0022] With the seventh aspect, since the front wall is formed to betilted downwardly and rearwardly, a stronger operation to shift thetorsion beam downwardly takes place, so that the effects of the sixthaspect are more certainly obtainable.

[0023] An eighth aspect is that, in the motor vehicle rear suspensionapparatus employing the sixth aspect, the lateral link is placed betweenthe front wall and the torsion beam.

[0024] With the eighth aspect, the operation of the lateral link in thesixth aspect can more certainly produce the effects of the sixth orseventh aspect.

[0025] Other objects and advantages besides those discussed above shallbe apparent to those skilled in the art from the description of apreferred embodiment of the invention which follows. In the description,reference is made to accompanying drawings, which form apart thereof,and which illustrate an example of the invention. Such example, however,is not exhaustive of the various embodiments of the invention, andtherefore reference is made to the claims which follow the descriptionfor determining the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a plan view showing a suspension apparatus for a motorvehicle according to an embodiment of the present invention; and

[0027] FIGS. 2 to 5 are side elevational views showing the suspensionapparatus where a portion is omitted from FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028]FIG. 1 shows a rear suspension apparatus for a motor vehicle suchas RV according to an embodiment, where reference mark 1R represents arear right-hand wheel and reference mark 1L denotes a rear left-handwheel. Designated at numeral 2 is a rear differential gear casecontaining a rear differential gear for differentially distributing adrive force to the rear right- and left-hand wheels 1R and 1L. Further,in front of the rear differential gear case 2 in forward and backwarddirections of a vehicle body, there is disposed a center differentialcase 3 housing a center differential mechanism for differentiallydistributing a drive force between front and rear wheels. A drive forcefrom a non-shown engine placed at a front section of a motor vehicle istransferred from the center differential case (gear) 3 and the reardifferential gear case (gear) 2 through right- and left-hand driveshafts 4R, 4L to the rear right- and left-hand wheels 1R, 1L. In thisembodiment, the motor vehicle is a four-wheel drive car.

[0029] The suspension apparatus for the rear right- and left-hand wheelsis equipped with a pair of right- and left-hand trailing arms 11 servingas suspension arm members (suspension components). Each of the trailingarms 11 substantially horizontally extends in the vehicle body forwardand backward directions, and its front end portion 11 a is supported bythe vehicle body to be rotatable about an axis running in the vehiclewidth direction so that the trailing arm 11 can freely swing up anddown.

[0030] Each of rear end portions 11 b of the pair of right- andleft-hand trailing arms 11 is rotatably supported by a torsion beam 12lengthily extending in the vehicle width direction. To both end portionsof the torsion beam 12, there are fixed wheel supporting members 13 forrotatably holding the rear right- and left-hand wheels 1R, 1L.Incidentally, it is also appropriate that the rear end portion 11 b ofthe trailing arm 11 is pivotally coupled directly to the wheelsupporting member 13. The torsion beam 12 is located to bypass the reardifferential gear case 2 to pass behind it in the vehicle body forwardand backward direction. Concretely, the torsion beam 12 is made of amaterial having a sufficient rigidity and formed to have a diameterproviding a sufficient rigidity, and its central portion 12 a positionedjust at the rear of the rear differential gear case 2 is bent or curvedrearwardly and upwardly in order to avoid the interference with the reardifferential gear case 2 and further to prevent a fall of a floor at arear side collision. The torsion beam 12 runs substantially straightfrom this central portion 12 a up to both end portions in the vehiclewidth directions (see FIGS. 2 to 5).

[0031] The central portion 12 a of the torsion beam 12 is bent to runalong an external shape of the rear differential gear case 2 anddisposed at the rear of the rear differential gear case 2, and further,curved upwardly to be at a position slightly lower than the verticalcenter position of the rear differential gear case 2 (see FIGS. 2 to 4).

[0032] As shown in FIGS. 2 to 4, the rear section of the reardifferential gear case 2 confronting the central portion 12 a of thetorsion beam has a curved portion 14 protruding rearwardly, and thiscurved section 14 has a peak portion 14 a whose substantial centerposition in vertical directions projects most rearwardly when viewedfrom a side. That is, the portion of this curved section 14, from theupper portion to the peak portion 14 a, protrudes smoothly andrearwardly, while the portion thereof from the peak portion 14 a to thelower portion is curved smoothly and forwardly.

[0033] At the rear of the torsion beam 12, there is disposed a laterallink 15 extending in the vehicle width directions. As shown in FIG. 5,this lateral link 15 is mounted such that its one end portion and itsother end portion are offset vertically to be tilted, and its lower endportion 15 a is connected to the torsion beam 12 while its upper endportion 15 b is coupled to the vehicle body. The connecting portions ofthe upper and lower end portions 15 b, 15 a of the lateral link 15 issupported so that the lateral link 15 can swing in a state where itsrotation axis is taken in a vehicle body forward and backward direction.

[0034] To the torsion beam 12, in the vicinity of both the end portionsthereof in the vehicle width direction, there are connected a pair ofright- and left-hand suspension dampers 16 and a pair of right- andleft-hand suspension springs (in this embodiment, coil springs) 17. Thatis, to the torsion beam 12, in the vicinity of each of the trailing arms11, a damper bracket 18 is fixedly located and a spring sheet 19 isfixedly placed at a slightly inside position in the vehicle widthdirection with respect to the damper bracket 18. In the damper bracket18, a lower end portion 16 a of the damper 16 is supported to be allowedto freely swing in a state where its rotation axis coincides with avehicle width direction, and an upper end portion 16 b of the damper 16is supported to be allowed to freely swing with respect to a floor frame20, so that the damper 16 can freely swing up and down. In addition, thedamper 16 is disposed to be tilted forwardly from the lower end portion16 a to the upper end portion 16 b (see FIG. 2).

[0035] A lower end portion of the coil spring 17 is placed in the springsheet 19, while an upper end portion of the spring 17 is brought intocontact with the floor frame 20 (see FIG. 3).

[0036] As shown in detail in FIG. 2, a floor panel 21 in the vehiclebody rear section is largely expanded protrusively and downwardly frombehind the lateral link 15 to define a recessed space 22. This recessedspace 22 is formed to run in a vehicle width direction, and formed sothat the whole assumes a rectangular configuration when viewed from theabove. For example, in the case of a triplex-row-seat car, when thethird row seat is removed, the seat can be accommodated (accommodated ina state where a seat cushion and a seat back are stacked in asubstantially horizontal condition). This recessed space 22 ischangeable in size and shape to accept a spare tire.

[0037] A front wall 22 a defining the recessed space 22 is graduallytilted rearwardly while extending downwardly, while a bottom wall 22 bextends in a substantially horizontal direction to form a generally flatsurface. The height of the front wall 22 a (the depth of the recessedspace) is set to substantially equal the central portion 12 a of thetorsion beam 12. Besides, preferably, the height of the bottom wall 22 bis set to be higher than the height of the center position of the heightdimension of the vertical curving of the central portion 12 a of thetorsion beam 12, which can prevent a fall of the floor at a rear sidecollision which will be mentioned herein later.

[0038] The torsion beam 12, the lateral link 15, a rear portion 27 c ofan exhaust pipe 25 and the recessed space 22 are disposed in order atthe rear of the rear differential gear case 2.

[0039] In FIG. 5, numeral 25 signifies an exhaust pipe extending from anengine, and a connection of a muffler 26 to this exhaust pipe 25 is madeon a side of the center differential case 3 and in front of the reardifferential gear case 2. The exhaust pipe 25 existing at the rear ofthe muffler 26 is formed curvedly to bypass the torsion beam 12 to passabove it. That is, in the exhaust pipe 25, its curved portion 27 curvedto bypass the torsion beam 12 comprises three portions 27 a to 27 c. Theportion 27 a is an intermediate portion located above the torsion beam12 and extending substantially straight in the forward and backwarddirection, the portion 27 b is a front portion extending from theintermediate portion 27 a to gradually lower forwardly, and the portion27 c is a rear portion extending from the intermediate portion 27 a togradually lower rearwardly.

[0040] Secondly, referring to FIGS. 1 to 5, a description will be madehereinbelow of a behavior of the torsion beam 12, that is, the rearright- and left-hand wheels 1R, 1L, at the rear side collision.

[0041] At the rear side collision, the vehicle body deforms by receivingan external force from a rear side, and the front wall 22 a of therecessed space 22 shifts forwardly. When the torsion beam 12 receives astrong external force in the forward direction by being pressed by thefront wall 22 a, because of the abrupt external force, the damping forceof the damper 16 increases and operates like a strut, and owing to theinclination of the damper 16, the torsion beam 12 is forcedly shifteddownwardly. In other words, the rear wheels 1R, 1L are shifteddownwardly to limit the fall of the vehicle body rear section.

[0042] Even if the lower end portion 16 a of the damper 16 tries toshift forwardly, since the damper 16 swings about its upper end portion16 b, the damper 16 becomes longer vertically, which acts to make thetorsion beam 12 shift downwardly.

[0043] Furthermore, since the curved section 14 of the rear differentialgear case 2 stands in opposed relation immediately before the torsionbeam 12, the torsion beam 12 trying to shift forwardly is guided by thecurved surface lower in position than the peak portion 14 a of thecurved section 14 to shift downwardly, thereby limiting the fall of thevehicle body rear section.

[0044] Still further, both the end portions of the torsion beam 12 inthe vehicle width directions are at lower positions than the centralportion 12 a, and hence, when the central portion 12 a being at therearmost position tries to shift forwardly, the torsion beam 12generates component forces for shifting both its end portionsdownwardly, and consequently, the torsion beam 12 shifts downwardly as awhole, thus limiting the fall of the vehicle body rear section.

[0045] Looking at the lateral link 15, as easily understood from FIG. 5,the forward or upward (also, forward and upward) shifting of the torsionbeam 12 shows a motion to shorten the length of the lateral link 15, andthe lateral link 15 acts as a strut. On the contrary, the downward(forward and downward) shifting of the torsion beam 12 takes a motionwhereby the lateral link 15 smoothly swings with its upper end portion(a portion rotatably supported with respect to the vehicle body) beingtaken as a rotating center.

[0046] As described above, the operation of the lateral link 15 makesthe torsion beam 12 easily shift downwardly, thus limiting the fall ofthe vehicle body rear section.

[0047] At the rear side collision, of the curved portion 27 of theexhaust pipe 25 bypassing the torsion beam 12, the rear portion 27 cplaced at the rear of the torsion beam 12 guides the torsion beam 12downwardly by its inclination, thus limiting the fall of the vehiclebody rear section. In addition, although the rear portion 27 c isdeformed so that the connecting portion with the intermediate portion 27a is bent, this deformation reduces the space necessary for the upwardshifting of the torsion beam 12.

[0048] At the rear side collision, the recessed space 22 assuming alarge volume protrusively comes above the torsion beam 12 to limit theupward shifting of the torsion beam 12. Moreover, due to the inclinationof the front wall 22 a of the recessed space 22, the torsion beam 12 ispressed forwardly by the front wall 22 a to be shifted downwardly.

[0049] Although the embodiment has been described above, the motorvehicle can be not only a four-wheel-drive car but also arear-wheel-drive car. Further, it is possible to properly select thebody configuration of the motor vehicle such as a general passenger carhaving a trunk compartment at its vehicle body rear section.

[0050] The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention the following claims are made.

What is claimed is:
 1. A torsion beam type rear suspension apparatus fora motor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein a central portion of a torsion beam in awidth direction of said motor vehicle is bent along a configuration ofsaid differential gear case, and is located at the rear of saiddifferential gear case, and a suspension damper placed between saidtorsion beam and a body of said motor vehicle is disposed in a state ofbeing inclined upwardly and forwardly.
 2. A torsion beam type rearsuspension apparatus for a motor vehicle having a differential gear casedisposed between rear right- and left-wheels, wherein a central portionof a torsion beam in a width direction of said motor vehicle is bentalong a configuration of said differential gear case, and is located atthe rear of said differential gear case, and wherein said differentialgear case has a curved section protruding rearwardly, and said centralportion of said torsion beam is placed at a lower position than a peakportion of said curved section.
 3. A torsion beam type rear suspensionapparatus for a motor vehicle having a differential gear case disposedbetween rear right- and left-wheels, wherein a central portion of atorsion beam in a width direction of said motor vehicle is bent along aconfiguration of said differential gear case, and is located at the rearof said differential gear case, and wherein said central portion of saidtorsion beam is formed to be at a higher position than both end portionsthereof in said vehicle width direction.
 4. A torsion beam type rearsuspension apparatus for a motor vehicle having a differential gear casedisposed between rear right- and left-wheels, wherein said torsion beamis connected to said vehicle body through a lateral link extending insaid vehicle width direction, and said lateral link is disposed to beinclined up and down in said vehicle width direction, with its upper endportion being connected to said vehicle body while its lower end portionbeing connected to said torsion beam.
 5. A torsion beam type rearsuspension apparatus for a motor vehicle having a differential gear casedisposed between rear right- and left-wheels, wherein an exhaust pipeextending from an engine is bent for bypassing said torsion beam to passabove said torsion beam, and extends to a rear section of said vehiclebody, and a portion of said exhaust pipe rearwardly extending from thecurved portion is disposed to run from above said torsion beam to belowsaid torsion beam to cross said torsion beam, and is inclined downwardlyand rearwardly.
 6. A torsion beam type rear suspension apparatus for amotor vehicle having a differential gear case disposed between rearright- and left-wheels, wherein a central portion of a torsion beam in awidth direction of said motor vehicle is bent along a configuration ofsaid differential gear case, and is located at the rear of saiddifferential gear case, and wherein a recessed space formed to a floorpanel of said vehicle body and enlarging protrusively and downwardly isplaced at the rear of said torsion beam, and the height of a lower endportion of a front wall defining said recessed space is set to exceedthe height of an upper end portion of said torsion beam.
 7. A rearsuspension apparatus for a motor vehicle as defined in claim 6, whereinsaid front wall extends at least from above said torsion beam to undersaid torsion beam, and is inclined downwardly and rearwardly.
 8. A rearsuspension apparatus for a motor vehicle as defined in claim 6, whereinsaid lateral link is placed between said front wall and said torsionbeam.